American Standard Code for Information Interchange.

A coding scheme whereby every character the computer can access is assigned an integer code between 0 and 127. (no ASCII is NOT 8 bits). When more than 127 characters are needed, the Unicode internet character set or one of its other subsets is used. ASCII can be defined as the first 127 codes in the Unicode set. A subtile but important point is that character set encoding has nothing to do with the actual shape of the characters being encoded.

Move your mouse over the entries in this table to see the decimal and hexidecimal value of each character:

   x0  x1  x2  x3  x4  x5  x6  x7  x8  x9  xA  xB  xC  xD  xE  xF 
0x NUL  STX  SOT  ETX  EOT  ENQ  ACK  BEL  BS   HT   LF   VT   FF   CR   SO   SI  
1x DLE  DC1  DC2  DC3  DC4  NAK  SYN  ETB  CAN  EM   SUB  ESC  FS   GS   RS   US
2x     !   "   #   $   %   &   '   (   )   *   +   ,   -   .   /
3x 0   1   2   3   4   5   6   7   8   9   :   ;   <   =   >   ?
4x @   A   B   C   D   E   F   G   H   I   J   K   L   M   N   O
5x P   Q   R   S   T   U   V   W   X   Y   Z   [   \   ]   ^   _
6x `   a   b   c   d   e   f   g   h   i   j   k   l   m   n   o
7x p   q   r   s   t   u   v   w   x   y   z   {   |   }   ~  DEL 

(the following table shamlessly stolen from http://www.cs.tut.fi/~jkorpela/chars/index.html)

Notes:

• The first column shows the widely used "control-something" name used for control codes. It relates to the fact that on a keyboard, it is often possible to generate a control code using the control (Ctrl, Ctl) key and a normal key.
• The column C0 of ISO 646 quotes the definition in that document, with typos fixed, and with references to characters and code positions changed to use Unicode names and modern terms.

Historical table

The following table lists the original names of Ascii control codes as defined in 1963.

Ascii 1963 assigned code position 126 to the ESC code. Later ESC was moved to position 27, and position 126 was assigned to tilde (~). Similarly ACK was moved from 124 to 6, making room for vertical line (vertical bar, |).

Note: The space character (blank, Ascii code position 32) is not discussed here. It can be classified and processed as a graphic character, or as a control character, or both, depending on context.

EOU: From FOLDOC. The mnemonic of a mythical ASCII control character (End Of User) that would make an ASR-33 Teletype explode on receipt. This construction parodies the numerous obscure delimiter and control characters left in ASCII from the days when it was associated more with wire-service teletypes than computers (e.g. FS, GS, RS, US, EM, SUB, ETX, and especially EOT). It is worth remembering that ASR-33s were big, noisy mechanical beasts with a lot of clattering parts; the notion that one might explode was nowhere near as ridiculous as it might seem to someone sitting in front of a tube or flatscreen today.

Sources:

• American Standard Code for Information Interchange ASA standard X3.4-1963 ("Ascii 1963"); note that it allocated ACK to code position 124 and ESC to code position 126
• C0 Set of ISO 646 in International Register of Coded Character Sets To Be Used With Escape Sequences
• The Unicode Standard Version 3.0

See also:

• http://www.cs.tut.fi/~jkorpela/chars/index.html An absolute tour de force on character (especially ASCII and Unicode) encoding. More than you ever wanted to know! History, etc... amazing...+
• In Windows 3.x: \Windows\charmap.exe

Also:

• Art

Questions:

• pushpa_man11 at STOPspamyahoo.co.in " what is the ascii value for the enter key" James Newton replies: ASCII codes are not the same as Keycodes. The PC/AT keyboard does not produce ASCII codes for every key presss. Each physical key generates a unique keycode even when there are more than one key with the same lable, as is the case with the Enter key. There are several different keycodes returned for Enter depending on which enter key (main or number pad) and on which other keys you press it with (shift, ctrl, alt). For the complete list, see http://techref.massmind.org/techref/si/arne/www/http/~mauricio/Kbdfaq.htm#KEYBOARDFAQ_038. Both Enter keys, when pressed by themselves, are translated into the ASCII code 13 (0x0D) at some point, although in some cases you will get ASCII code 13 and 10 (carriage return and line feed) from each Enter key press.+

  +

Comments:

• evanejk at STOPspamgmail.com " Wow this is great. The best converter I've found." James Newton of Massmind replies: Thank you.+

  +

OCT 31 = DEC 25, for those who ever wonder what Haloween has to do with Christmas. +

Code:

• //Here is the basic Javascript used to display hex values from decimal
  function hexDigit(num) {
      if (num < 10) {
          return num;
          }
      else {
          if (num == 10) { return "A" }
          if (num == 11) { return "B" }
          if (num == 12) { return "C" }
          if (num == 13) { return "D" }
          if (num == 14) { return "E" }
          if (num == 15) { return "F" }
          }
      }
  
  function hexByte(byte) {
      var first = Math.floor(byte/16);
      var second = byte - first*16;
      return ""+hexDigit(first)+hexDigit(second);
      }
  

  +

Better code: The Number.toString() function can accept an optional base parameter. So the hexByte function could simply return byte.toString(16). Or to preserve two character formatting. return "0"+byte.toString(16).substr(-2) +

  .